The salt marsh and its root layer
Between the dump and the bay our plan
is to interpose a salt marsh. The topmost
layer, the root layer, is to function
as a septic tank. Aerobic and anaerobic
phases alternate with each pulse of
Aerobic respiration and sulfate reduction
dominate the activity.
Rhizosphere, living machine, septic tank
- The root system of cordgrass is maintained
in a seasonally varying biomass by the
carbon cycle of the salt marsh.
It is fractoid (approximately fractal) part
of the upper layer of the salt marsh, comprising
up to 50% of the volume, and about
50% of the biomass. It extends a few millimeters
outward from each root surface, and appears
red from ferric oxide accumulation
due to oxygen diffusion down the stems
and rhizomes of cordgrass.
Thus oxidized and reduced regions are
closely packed in the root layer.
(Pomeroy, 1981, p. 18)
- We assume (provisionally) that the
cordgrass biomass and rhizosphere are
unaffected by the leachates.
- The biomass of cordgrass, and the carbon
cycle, may be modeled by the complex
dynamical model, MRSH1V6, of the
Sapelo Island marsh (Pomeroy, 1981, Ch. 9)
or some similar model, or from data taken
from a salt marsh closer to Pelham Bay.
- The fate of a COC in a single pulse
of leachate is a decrease in concentration
due to diffusion-reaction mediated by
- For one of the COCs, ammonium,
the bacterial agents will be those
of the nitrogen cycle.
- This diffusion-reaction system,
for a single tidal pulse, is the
goal of our model.
For these geobiochemical reactions,
we assume Monod dynamics with a
compartment of unknown bacteria.
- In sum, we regard the upper (root)
layer of the cordgrass marsh as a living
machine, or geobiochemical reactor,
for the bioremediation of COCs pulsing
our of the dump, and we simulate their
removal individually, that is, one COC at
Revised by Ralph Abraham 16 August 1998